This was copied from the SharePoint Farmers Almanac by Shane Young

• Export Farm Solutions

(Get-SPFarm).Solutions | ForEach-Object{$var = (Get-Location).Path + "\" + $_.Name; $_.SolutionFile.SaveAs($var)} 

• Import Farm Solutions

Get-ChildItem | ForEach-Object{Add-SPSolution -LiteralPath $_.Fullname} 

• Deploy Farm Solutions

Get-SPSolution | ForEach-Object {If ($_.ContainsWebApplicationResource -eq $False) {Install-SPSolution -Identity $_ -GACDeployment} else {Install-SPSolution -Identity $_ -AllWebApplications -GACDeployment}}